


Two Reasons

by Interverse



Category: Undertale (Video Game)
Genre: Alternate Universe - Underswap (Undertale), Ecto-Genitalia (Undertale), Ecto-Tongue (Undertale), I wrote this on a whim- don't mind me, M/M, Meaning that there are TWO Swap Sanses, Plot What Plot/Porn Without Plot, The first is called Blue and is the 'normal' Swap Sans, Threesome - M/M/M, Twin Brother Sanses AU, While the second is called Berry because there are no other good names
Language: English
Status: Completed
Published: 2019-03-12
Updated: 2019-03-10
Packaged: 2019-11-14 21:09:48
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 2,042
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18060176
Author URL: https://archiveofourown.org/users/Interverse/pseuds/Interverse
Summary: Blue and Berry are known to be...energetic, even in the middle of the night. Stretch has mixed feelings about this.





	1. Apart

Swap Sanses were known for their energy, and that was no exception here. It kept them going through all of their busy days with such enthusiasm and resolve, but that was not enough to drain them, so consequently, both of the twins were frequently awake in the middle of the night, staring into one another’s bright cyan eyelights. This was one of those nights.

 

The boredom didn’t last long. Berry’s hands found their way to Blue’s iliac crests, where they roughly squeezed and pulled a grunt from their twin. Blue returned the grip, not at all surprised when one of his brother’s hands slipped into his pants and palmed at his pubis, coaxing his magic to the area. He retaliated with the same treatment, and as they were finding to happen quite frequently, were soon manifested and hard in one another’s grip.

 

They scooted closer to each other simultaneously, groaning when their magic pressed together through their clothes. Neither of them were willing to back down into a position that could be seen as submissive, so they were left to thrust against each other, foreheads pressed together and hands groping everything they could reach. They panted, hot, rugged breaths blowing over each other’s clavicles and upping their desperation even further.

 

Small, clumsy hands reached down to fiddle with their pants, and they whined when their cocks were freed and allowed to touch directly. They sped up their movements, precum dribbling from their magic and making the motions easier and far more satisfying. 

 

They had been trying to hold back, always caught up in competition, but they broke at the same time, moans spilling out from between their teeth and their thrusts growing messy. They loved each other so much. They were so similar, and yet never got bored with one another. Everything was always new and exciting, even though they must have done this a thousand times by now. 

 

They had leaked so much at that point that small squelching noises could be heard from where they ground together above their vocalizations of their pleasure and love for one another, and this only drove them further, their movements becoming so rough and so erratic that the bed creaked beneath them. They came unanimously as they always did, crying out and grabbing each other hard enough to bruise as their magic pulsed and expelled rope after rope of bright blue ectoplasm all over them. But they didn’t stop. They kept thrusting, through every single shot of their cum and even after they had ceased, only slowing when the sensitivity grew uncomfortable.

 

They knew this wouldn’t last long, and as they looked into each other’s eyes, panting in the afterglow of their joint climax, they knew something else, too. Help would be needed from a third party in order for them to get back to sleep, lest they be here all night.


	2. Together

Stretch woke when his bedroom door creaked open, begrudgingly cracking open an eyesocket and watching with blurry vision as his brothers slunk into his room before closing the door again. He thought that they might have just wanted to sleep in his bed with him, as they were known to be clingy, so he closed his eye again, sighing and starting to drift back to sleep. 

 

He could tell which of his brothers was which, despite them looking and sounding almost identical. It was some instinctive feeling he got in his Soul, so he smiled through his sleepiness when Blue wiggled under the blankets and pressed up against his back, and when Berry plastered himself to his front. They nuzzled at him, and Stretch was just about to give in to the warmth of his bed and the darkness of his room again before something sent his eyes flying open.

 

Two warm, very distinctive objects were pressing against him, and he flicked his eyelights to Berry’s in his surprise. The small skeleton softly shushed him, reaching up under Stretch’s shirt to stroke at his ribs while Blue gently began to massage one side of his pelvis. Ah, so it was one of those nights. The twins rarely came to him for relief in the middle of the night, not wanting to bother him in his sleep, so they must have been particularly restless this time.

 

His breath hitched when Blue shifted, his rigid length grinding against his sacrum and sending his magic rocketing down to his pelvis. He was not looking for this. He just wanted to sleep. But alas, he was fighting a losing battle, and he didn’t want to reject his brothers so blatantly. He certainly wouldn’t be at all opposed to this at almost any other time, but his reluctance for it happening now was quickly slipping from his grip. Blue and Berry were so steady and so warm against him, smelling of coconuts and of home, not to mention that they were both rock hard and-

 

Stretch’s train of thought came to a screeching halt when Berry’s cock managed to gain direct friction against his pubis, and the magic that had been simmering beneath the bones there seeped out. Berry made a pleased noise, and with a heavy swallow, Stretch formed the magic and made the rest of his body in a way to accommodate both brothers. 

 

Their enthusiasm skyrocketed, and they sped up, their hands flying to grab his summoned hips and thighs rather than touch him more decisively. Stretch didn’t care, not when Blue’s cock pressed into the cleft of his ass and Berry’s ground against his clit. While he didn’t bother to take off his usual orange sweatshirt before going to bed, he’d never slept with any pants, so the sudden magic-on-magic contact was utterly overwhelming. He whimpered, a deep, burning need blooming in his body. His brothers were letting out the sweetest, softest moans, and tears pricked at the back of his sockets at the intensity of it. They weren’t even really touching him yet, but he could already feel warm fluids dribbling down between his thighs. 

 

He must have made a particularly desperate noise, because Berry tilted his head to look at him, face flushed and mouth pulled into a mischievous grin. “What’s wrong, Papy? Do you want us to stop?”

 

Stretch hated and loved the teasing all at once, but there was no going back now, and he had no time for playing games. “No, f-fuck, please…”

 

“Please, what?” Blue purred into his shoulder, ghosting his fingertips over the tingling magic of his ass. 

 

Stretch nearly sobbed out his answer. “Please… fu-aah-!” He cut off when Berry’s magic managed to pull back his clitoral hood with one of its thrusts and catch on the swollen bead of magic unobstructed, but he gathered himself and tried again. “F-Fuck… me…”

 

“You sure?” Both twins asked him, their voices strained.

 

While it was infuriating and bordering on entirely unpleasant, it was sweet, that they did this. They said that they liked to make him beg every time because the enthusiastic consent made them feel more comfortable with such intimate activities with him. They were closer to each other than they were to him, so they were careful. 

 

But he didn’t want them to be. He wanted them to take what they wanted, no questions asked. “I-I’m sure…”

 

The twins groaned into his body, their hands traveling between his legs and swiping up all of the fluids he was leaking, their small fingers deftly spreading the lubricant up along his labia and over his hole. When the dexterous phalanges pressed at his entrances and made their way inside him, he allowed his eyelights to roll back in his head, little tremors traveling up his body while they relentlessly prodded around inside of him, searching for his sensitive spots and finding them quickly.

 

He whined pitifully, entire body filled with aching need. Luckily, the twins had never been known for their patience. They extracted their hands soon enough, and replaced them with their magic. Stretch cried out when they thrust their way inside of him, but the sound was cut short when two of Berry’s fingers shoved themselves into his salivating mouth and pressed down into his tongue, rendering him silent. He could taste himself on his brother’s bones, and only able to whine and groan deep in his throat, he lay there as they began to rut into him, fast and hard and with no hesitation. 

 

His eyelights must have blinked out of his sockets, because he couldn’t see anything anymore, despite his eyes being stretched wide with the overwhelming sensations cascading through his body. His brothers were so warm and hard inside of him, stretching his magic to its limits and reaching deeper than he was aware he was capable of hosting them. One of Blue’s hands slunk around his hip, and he nearly choked on his breath when a couple of fingers began to roughly press and rub at his clit.

 

His hearing must have betrayed him too, because he was all of a sudden aware of the noises surrounding him. His brothers’ desperate, throaty moans, the wet, relentless sounds of their magic plunging into and then dragging out of his, and his own ragged breaths. This only made him worse off. Blue pinched his clit and he nearly bit down on Berry’s fingers, the knowledge that he couldn’t go on becoming more and more prevalent in his mind. There was nothing he could do, there really wasn’t. Nothing was in his favor. He could have cum already, and not even noticed it, because of how intense everything already was. For all Stretch knew, he had been lying here for hours on end while his brothers pounded into him and coaxed him into climax dozens of time, and at one point, it grew to much and he had blacked out.

 

But even if that was the case, when his orgasm crashed through him, it was just as overwhelming as he had anticipated it to be. He shook. He shook so hard his bones literally could have rattled if he weren’t so immobile between the twins’ bodies, and his voice got locked in his chest. Waves of pleasure bordering on pain rolled through every inch of his body, each one more intense than the last. Blue and Berry didn’t stop, or slow down, but they grew sloppy. Their thrusts were erratic and uncalculated, and they might have screamed that they loved him, but he couldn’t be sure, not now.

 

He was just beginning to get over the sharpest parts of his climax when they slammed into him for one final time with moans so loud they could easily be classified as screams, releasing so much hot ectoplasm so deep inside of him that he could have been convinced he had been thrown in a pot of boiling water. But he loved it.

 

He barely noticed when the warmth of his brothers’ labored breathing was no longer soaking into his body, only vaguely registered it when they extracted themselves from him, and was no more than slightly aware of the shower of light kisses from two mouths that were pressed against his skull before a weight clambered off of the bed. He might have heard his door creak, and might have heard a set of footsteps traveling down the hall, but he wasn’t ready to make any bets on it.

 

He finally came to when a small hand delicately caressed his face. He blinked and looked up to where Blue was standing over him. “Papy,” the Sans murmured, “Are you alright?”

 

Stretch would have nodded or smiled if he had the energy, but he was sure his eyelights were blazing with enough of the happiness and love he was feeling to get the message across. “Yes.”

 

“Do you want me to help clean you up? I could give you a massage, or make you something to eat.”

 

Stretch sighed. “No. I just want to sleep.”

 

Blue giggled. “Right. We love you, you know?”

 

“I know.”

 

And with that, Blue left to join his twin in their bed, and Stretch was left alone. But despite the feeling of thick blue cum leaking from his body and soaking into the sheets, he was contented. For exactly two reasons.


End file.
